I just wanted to say that I agree with the other ladies!!

I had a similar experience with a wedding I was a BM in. I did everything I could to make it all about her. Spent a ton of money for her wedding, threw her a fancy shower, and was truely happy for her. Well, my FH proposed 3 weeks prior to her wedding and she thought I would have upstaged her or something by it. Anyhow, to make a long story short I am convinced that sometimes you can't get the bridezilla out of the bride even after they are married!!

I really hope your sister is nothing like my former friend. I hope everything works out for you!